The present invention relates to a mobile terminal for transmitting emergency information by compressing the information without degrading the details when the emergency should be reported to an information service centre or an emergency centre (hereinafter referred to as a xe2x80x9ccentrexe2x80x9d), and an emergency reporting system for receiving the information at the centre from the mobile terminal and then provides an emergency service from the centre to the mobile terminal.
Cellular phones having a position detecting function such as global positioning system (GPS) or movable terminals having a sensor for detecting an abnormality or emergency have been downsized and become inexpensive thanks to technical progresses. Reliability including shockproof characteristic of those mobile terminals has been also improved. Such a mobile terminal in a small body is installed in a vehicle and used as an emergency reporting system when a traffic accident occurs. Another small mobile terminal is shaped into a pendant and used as a man locating system for a user having a chronic illness such as a heart disease to inform a centre of his or her location.
A location sending device as such a mobile terminal is disclosed in Japanese Patent Application Non-Examined Publication No. H06-18648. This location sending device, as shown in FIG. 1, measures a present position using GPS satellite 101, and GPS receiver 102 acquires resultant positional information comprising a latitude, longitude and altitude. This information is measured periodically or at spatial intervals when the mobile terminal moves, and the track information between a plurality of locations is stored in ring-buffer-memory 103 cyclically.
When an abnormality or emergency occurs, or when a centre issues an emergency request, the mobile terminal produces a transmission signal using a given protocol through the following method: a transmission-starting-time supplied from timer 104 and a mobile terminal ID code held by ID-code-holder 105 are added to the track information between plural positions immediately before the instant position. This track information is selected from other track information stored in ring-buffer-memory 103. The transmission signal is formed to have a given signal format at transmission-signal-forming section 107 following a transmission-signal-format provided by transmission-signal-format-holder 106. Radio transmitter 108 modulates a high-frequency-carrier-wave with the transmission signal, and outputs the positional data of a sender from antenna 109 to the centre.
When the centre receives the track information from the mobile terminal, a terminal ID of the centre identifies the sender by checking his membership. At the same time, the track information is plotted on a digital map displayed on a console in the centre, so that the centre can be informed of the track-record of the mobile terminal. When the data transmission from the mobile terminal to the centre is completed, audio signals replace data signals in communication and thus a voice communication between a terminal-owner and the centre takes place.
However, a conventional system takes a rather long time for the communication because all the track information of a mobile terminal including track records between plural points and a terminal ID must be transmitted. In the case of employing a *centre differential GPS method (C-DGPS method), the information about 500 points needs as much as 29 kilo Bytes, and it takes about 30 seconds when the information is sent at 9,600 bps. This time-consuming transmission has been a bottleneck for tracking and searching a mobile terminal. *Centre differential GPS method modifies the information of latitude and longitude acquired by the mobile terminal with error correction, and realises a highly accurate measuring such as a measuring error falling within a 10 to 30 meters range.
In the case of employing a method other than C-DGPS method, the information about 500 points needs approx. 9.5 kilo-Bytes, and it takes about 10 seconds for transmission; however a measuring error becomes as large as several hundreds meters. The centre cannot exactly identify the position of the mobile terminal with this poor positional accuracy.
An emergency reporting system used at a traffic accident or a man-locating system for reporting a heart attack, affects people""s lives and thus the system needs a high-speed process as well as highly accurate tracking of the mobile terminal""s position. However, the conventional system as discussed above has a problem that the high-speed and high-accuracy are not compatible.
The present invention addresses the problems discussed above and aims to shorten the communication time by coding data when positional information of plural points is transmitted. Further, the present invention aims to transmit positional data within a short time and with a high accuracy responding flexibly to travelling of a mobile terminal.
The present invention thus concerns an emergency reporting system as defined in the appended claims.
Thanks to these features it is possible to keep a positional accuracy, and this structure can encode the transmission data using relative-information thereby shortening the data transmission time.
An information service centre receives the data sent from the mobile terminal, decodes the data responsive to the compression or coding format of the data received, and supplies various services depending on emergency requests including an accident and a sudden illness. As a result, the centre can supply services within a short time for any compression method.